A communication system can be seen as a facility that enables communication sessions between two or more entities such as fixed or mobile communication devices, base stations, servers, machine type communication devices and/or other communication nodes. A communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols can define the manner how various aspects of communication such as access to the communication system and feedback messaging shall be implemented between communicating devices. A communication can be carried on wired or wireless carriers. In a wireless communication system at least a part of communications between stations occurs over a wireless link.
Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). A wireless system can be divided into cells or other radio coverage or service areas provided by a station. Radio service areas can overlap, and thus a communication device in an area can send signals to and receive signals from more than one station.
A communication system can be accessed by means of an appropriate communication device. A communication device of a user is often referred to as user equipment (UE) or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling receiving and transmission of communications such as speech and data. In wireless systems a communication device provides a transceiver station that can communicate with another communication device such as e.g. a base station and/or another user equipment.
An example of communication systems is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP) and referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. A further development of the LTE is often referred to as LTE-Advanced. The various development stages of the 3GPP LTE specifications are referred to as releases.
Feedback information from communication devices is needed by the network. Feedback reports can be periodic or aperiodic. Periodic feedback is considered an important component of LTE feedback mechanism and applies the design principle of semi-static and periodic configuration the different feedback messages where the user equipment (UE) follows a predefined pattern of feedback messages. Physical Uplink Control Channel (PUCCH) is a dedicated channel used for the periodic feedback messages and continual tracking of channel state information (CSI). The CSI can include elements such as Channel quality indicator (CQI), Precoding matrix indicator (PMI), Precoder Type Indicator (PTI) and Rank indicator (RI). Compared to aperiodic feedback, an advantage of periodic feedback is that it does not need to be triggered by an uplink (UL) grant because of the semi-statically configured PUCCH resource for the feedback messaging.
More advanced transmission schemes can become increasingly desirable with the technical evolution. More advanced transmission schemes might benefit from support of more flexible feedback schemes. For example, multipoint schemes such as Coordinated Multi-Point Transmission (COMP) might benefit from additional feedback information, in particular inter-cell channel state information (CSI) feedback support. Currently the periodic channel state information (CSI) feedback can only be transmitted in the pre-assigned resources on PUCCH following a pre-configured pattern of different feedback messages. Configuration for periodic feedback is provided through radio resource control (RRC) signalling for a long period of time. Hence, sometimes PUCCH resource can become reserved even if it is not necessary. A periodic feedback can be inflexible in the sense of both resource allocation and feedback content.
Aperiodic feedback messaging can be used to compensate for the inflexibility of the periodic feedback. LTE Release 8 suggests aperiodic CSI-only reporting on Physical Uplink Shared Channel (PUSCH) to support uplink control indicator (UCI) PUSCH transmission. However, the inventors have recognised that use of aperiodic feedback of the current LTE mechanisms may not always be suitable, in particular where only a small number of dynamic feedback bits is needed. For example, on LTE aperiodic feedback must be transmitted with UL PUSCH, and therefore needs to be triggered by an UL grant. Although this can provide improved flexibility, use of the PUSCH can provide certain disadvantages. Use of aperiodic PUSCH feedback can waste UL resources since the resource allocation granularity can be too coarse. PUSCH granularity is one physical resource block (PRB) which can be excessive for instantaneous (e.g. wideband) feedback which typically consists of only about 10 bits. Also, dedicated separate UL grant downlink control indicator (DCI) needs to be transmitted just to trigger the CQI only PUSCH, and thus the overhead on the Physical Downlink Control Channel (PDCCH) is increased.
It is noted that the above discussed issues are not limited to any particular communication environment, but may occur in any appropriate communication system with retransmission mechanism and comprising a plurality of reception points.